Flame-holding and transition control means for pot-type oil burner



Feb 1957 I G. L. HERSHEY ETAL 3,303,863

FLAME-HOLDING AND TRANSITION CONTROL MEANS FOR POT-TYPE OIL BURNER FiledJuly 9, 1965 3 Sheets-Sheet 1 INVENTORS: GERALD L, HERSHEY FRANK A. LOWEATT'YS Feb 1967 G L HERSHEY ETAL 3, 03,

FLAME'HOLDING AND TRANSITION CONTROL MEANS FOR POT'TYPE OIL BURNER FiledJuly 9, 1965 3 Sheets-Sheet 2 HIGH FIRE OOOOOOOOOOOOOOOOO O 00000 5OINVENTORS.

GERALD L. HERSHEY FRANK A. LOWE BY: flaw m fh gkdfmw, l e/m uad AT T Y SFeb. 14, 1967 G. 1.. HERSHEY ETAL 3,303,868

FLAME-HOLDING AND TRANSITION CONTROL MEANS FOR POT-TYPE OIL BURNER FiledJuly 9, 1965 3 Sheets-Sheet :3

INVEN'IORS: GERALD L. HERSHEY FRANK A. LOWE ATT'YS BY: fiuugm Giul a, a

United States Patent FLAME-HOLDING AND TRANSITION 0NTRGL MEANS FORPOT-TYPE 01L BURNER Geraid L. Hershey and Frank A. Lowe, Wichita, Kans.,assignors to The Coleman Company, Inc., Wichita,

Kans., a corporation of Kansas Filed July 9, 1965, Ser. No. 470,812 19Claims. (Cl. 158-91) This invention relates to flame-holding andtransition control means for pot-type oil burners. This invention isparticularly adapted for use with vaporizing burner pots employing agravity oil feed and a regulated forced combustion air supply. While theimproved pot-type burners of this invention are particularly designedfor use in furnaces installed in mobile homes, the burners are also welladapted for other furnace or space-heating uses.

Pot-type oil burners have been known and used for many years, and manyforms and modifications thereof have been proposed. A recently proposeddesign is described in Mueller Patent 3,147,796. While the presentinvention was developed entirely independently of the design of theMueller patent, many of the features of the present invention can beregarded as constituting improvements thereover.

Pilot housings, such as the one described in the cited Mueller patent,have been proposed in various forms for use with pot-type burners, asillustrated, for example, by Miller et al. Patent 2,448,148, Huston etal. Patent 2,460,- 013, and Jenson et al. Patent 2,699,820. While theenclosure of the fuel inlet with a pilot housing is desirable forholding and maintaining the flame, particularly at pilot fire rates, thehousing may tend to cause a smoky or sooty flame during the transitionfrom pilot fire to intermediate or high fire rates. The flame may alsotend to pulse or bounce during transition periods. A recirculated typeflame, where combustion products are mixed with the oil vapors and airwhile avoiding a large excess of air, is particularly subject to smokingand/or pulsation during transition periods. Pot-type burners haveoperated reasonably satisfactorily at either pilot, intermediate, orhigh fire rates, but no pot-type burner has heretofore been providedwhich is cap-able of achieving stable, sootless combustion at all firerates from pilot to high fire, or which is capable of producing asootless, nonsmoky fire under pilot fire rates or during the transitionfrom pilot fire to intermediate or high fire rates.

Pilot housings fomed of sheet metal, as shown, for example, in HustonPatent 2,460,013 and Jenson et al. Patent 2,699,820, may not besatisfactory because of the unequal heating and cooling of the thinmetal walls of the housing, particularly the top wall where the pilotflame heat is concentrated. A heavy cast metal construction can be used,but this is more expensive to manufacture. Such a cast metalconstruction is illustrated by Mueller Patent 3,147,796.

Still another problem is that of the tendency of the flame to flutter orpulsate under pilot fire conditions within the pilot housing.Heretofore, the exact nature of this problem has not been recognized orunderstood.

Another problem encountered with pot-type burners is that of flooding.Where the oil is fed by gravity to the burner pot, it is common toemploy a constant level valve to regulate the supply of fuel. Where thebottom of the burner has a dished configuration, sloping toward thecenter, under some conditions of operation a substantial volume of oilcan accumulate. With this flooded pot" condition, it may take as long asthirty minutes for the oil in the burner, plus that coming in from theconstant level valve, to be consumed at a point Where the burner isfunctioning normally; During this flooded pot burn-off, excessive smoke,soot, noise and heat are produced in the unit.

It is a general object of the present invention to provide a pot-typeburner of improved construction which substantially overcomes theproblems and difliculties described above. More specifically, it is anobject to provide an improved flame-holding and transition control meansfor a pot-type burner which is capable of achieving stable,substantially sootless, flame at all fire rates from pilot to high fire,and which also provides for smooth transition between fire rates withoutbounce or flame pulsation and without undue sooting or smoking. Aspecific object is to provide a pilot housing which achievessubstantially sootless combustion at pilot fire rates. Another specificobject is to provide means associated with the pilot housing forreducing flame fluctuation or pulsation at pilot fire rates. Stillanother specific object is to provide a burner pot construction whichreduces or minimizes the problem of pot flooding and the prolongedperiod of burn-off after flooding. Finally, it is an object to provide aburner which accomplishes the results just described while operatingquietly under varying draft conditions that may be imposed upon it.Further objects and advantages will be indicated in the followingdetailed specification, such as the design feature which permits thepilot housing to be formed of sheet metal.

This invention is shown in an illustrative embodiment in theaccompanying drawings, in which FIGURE 1 is an elevational perspectiveview, with some portions thereof being broken away and shown in section,of a pot-type oil burner embodying the features of the presentinvention;

FIG. 2 is a top plan view of the pot burner of FIG. 1, with part of theupper flame ring being broken away to more clearly show the pilothousing;

FIG. 3 is a side elevational view, taken in section, of the same burnerpot;

FIG. 4 is a fragmentary sectional view of the pilot housing taken online 44 of FIG. 3; and

FIG. 5 is a fragmentary sectional view of the pilot housing taken online 55 of FIG. 3.

Looking first at FIG. 1, there is shown a burner pot designatedgenerally by the number 10, which has an open top, a closed bottom 11,and a circumferential side wall 12. Side wall 12 provides air inletperforations at levels above the lower portion of the pot, such as therow of primary air inlet perforations 13, 14, and 15, and the row ofsecondary air inlet perforations 16.

In the illustration given, the perforations within each of the rows 13,14, 15, and 16 are evenly spaced, and the perforations are. horizontallyaligned, except for the perforations in row 16, which are tippedupwardly, as shown more clearly in FIG. 3. The perforations 13 introduceair into the lower portion of the pot beneath control ring 17, whileperforations, 14, 15 and 16 introduce air into the upper portion of thepot above control ring 17. The perforations 16 introduce air in anupward direction adjacent the inwardly-extending portion of the upperflame ring 18, which provides an outer flange portion 1811 that isreceived on the outwardly-extending flange 12a of the pot side wall, andis attached thereto by spot welding. In the illustration given, andpreferably, the upper flame ring 18 provides an inwardly extendingportion 18b which slopes inwardly and upwardly. If desired, the outerportion of flange 18a may be provided with mounting holes 19, as shownin FIGS. 1 and 2.

In accordance with the present invention, there is provided a pilot firezone 20, including a mixing zone in the outer portion thereof, which islocated adjacent a side portion of bottom 11, and extends toward thecenter of the bottom. Preferably, the outer end of zone 20 is closed bypart of the lower portion of side wall 12, which includes theupwardly-extending portion of bottom 11. A housing designated generallyas 21 is mounted within the lower portion of the pot, and provides wallmeans enclosing the top and sides of the pilot fire zone 20. In theillustration given, housing 21 has vertically-extending side walls 21aand 21b, and a flat top wall 21c. Housing 21 has an open inner end 22 ofrestricted cross section as compared with the cross section of thehousing. Preferably, the side walls 21a and 21b converge in an inwarddirection, and top wall 21c slopes downwardly and inwardly, therebyprogressively decreasing the cross ection of housing 21 from the outerto the inner portion thereof.

It is not necessary for housing 21 to be sealed to the sides or bottomof the burner. In the illustration given, housing 21 is mounted by meansof tabs 23 which extend upwardly from the outer end of top wall 210 andare connected to the side wall 12 by any suitable means, such as rivetsfor permanent attachment, or bolts where it is desired to make housing21 readily removable. The sides 21a and 21b of the housing may extenddownwardly into a recess 24 formed in the outer portion of the bottom.

It has been found that the operation of housing 21 can be improved byincorporating therein verticallyextending baffle means dividing theouter portion of the pilot fire zone into at least twoinwardly-extending passages. One of the passages should convergeinwardly to an outlet within the housing of restricted cross section,while the other of the passages enlarges inwardly to an outlet withinthe housing of enlarged cross sec-tion. In the illustration given, twolaterally-spaced, verticallyextending baffles or deflectors 25 and 26are provided within the outer portion of the pilot fire zone 20. Asshown more clearly in FIGS. 4 and 5, the deflectors 25 and 26,respectively, have attachment flanges 25a and 26a which are rigidlyconnected to the underside of top wall 210 by spot welding. As shown inFIG. 4, the baffle walls 25 and 26 incline inwardly and downwardly, sothat the passage 27 therebetween converges in crosssection-al areatoward the restricted opening 28 at the inner end of passage 27. Theside passages 29 and 3t) enlarge toward their respective inner ends 31and 32. Preferably, the outer ends 33, 34 and 35 (FIG. respectively, ofthe passages 29, 28 and 30, as well as their inner ends 31, 28, and 32,are in open communication. In the illustration given, the outer ends ofbaflles 29 and 3t) terminate at spaced distances from the burner sidewall 12, which includes the upwardly-extending portion of bottom 11, toprovide the desired open flow communication, and the inner ends of thepassages terminate within housing 21, as shown in FIG. 5.

For cooperation with housing 21 and the baffles and 26, there isprovided separate oil and air inlet means communicating with the outerportion of the pilot fire mixing zone 20. In the illustration given, theoil inlet means comprises a pipe 36 which has an inner section 36acommunicating with an opening 37 in the lower portion of wall 12, or,more specifically, in that portion of side wall 12 provided by theupwardly-extending portion of bottom 11. The section 36a may be in theform of a nipple which is connected to wall 12 by brazing, and whichprovides a threaded connection with the pipe 36, which may be a pipeelbow for connection to a longer oil supply pipe.

Preferably, the oil inlet opening 37 is located immediately above theadjacent portion of bottom wall 12, and the terminal section 36a of pipe36 is inclined outwardly and downwardly with respect to the horizontal.The angle of inclination is of importance, and preferably is within therange of from 20 to 50, for example, an inclination of with respect tothe horizontal.

In the illustration given, the air inlet means to the pilot fire zone 20comprises a row of perforations 38 which are located in side wall 12just below the outer end of housing top wall 21c, as shown in FIGS. 3and 5. Preferably, the perforations 38 are tipped downwardly so as totend to direct the incoming air toward the bottom of zone 20. As shownin FIG. 5, some of the perforations are aligned with the side passages29 and 30, but most of the perforations are aligned with the centralpassage 27.

When housing 21 is formed of sheet metal, as preferred, it is desirableto provide a protector strip 39 which is supported adjacent theunderside of the housing top wall 210 by means permitting the protectorstrip to expand and contract independently of the top wall. Strip 39 maybe conveniently formed of sheet metal. In the illustration given, theouter end portion of strip 39 is rigidly attached to the top wall 210,such as by spot welding, and the inner end portion of the strip isturned upwardly over the inner end portion of top wall 210 to form aslidable support therefor, as shown more clearly in FIGS. 2 and 3. Theinner portion of strip 39 is therefore free to expand laterally andinwardly on being heated without causing distortion of top wall 210, thedirection of expansion being indicated by the arrows in FIGS. 2 and 3.

The operation of the pilot fire zone 20 is further improved by providingan oil-holding depression or sump 40 adjacent the oil inlet opening 37.Preferably, sump 49 comprises the lowest portion of bottom 11. It isdesirable to mount a flat, non-combustible wick 41 within sump 40. Inthe illustration given, the wick 41, which may be formed of asbestosfibers, is held in place by a metal strap 42 which is secured to bottomwall 11 by spot welding. Preferably, wick 41 extends up to the oil inletopening 37 so that the oil as it enters will fall on the wick 41.

The operation of burner 10, particularly during the transition frompilot fire rates to high fire rates, is significantly improved Where thehousing 21 extends only part of the way toward the center of the bottom,and a vertically-extending ring, such as the ring 42, encloses a centralzone 43 in the lower portion of the pot. One side of the ring 42 has anopening therethrough in direct communication with the open inner end 22of the housing 21. In the illustration given, the ring 42 is U-shaped,and provides vertically-extending flanges 42a and 4217 which areattached to the forward ends of the housing side walls 21:: and 2111.One preferred means of attachment is by means of rivets, such as therivets 44 and 45, that have one end connected respectively to theflanges 42b and 42a and the other end slidably and pivotally received inthe grooves 46 and 47. The sliding hinge connection thereby providedfacilitates the insertion of the assembly of the housing 21 and the ring42, and the conformity of these parts to the contoured shape of bottom11.

While ring 42 may have imperforate side walls, the operation of theburner is improved where a plurality of openings 48 are provided in thelower portion of the ring 42. The openings 48 provide communicationbetween the bottom of the central zone 43 and the surrounding peripheralzone 49 beneath the control ring or baffle 17. It has been found that aspecific construction of the control ring 17 cooperates in aparticularly effective manner with the pilot flame ring 43, and thisconstruction will now be described.

As shown more clearly in FIGS. 1 and 3, the control ring 17 is in theform of an annular baffie plate, which has its outer portion supportedagainst the burner side wall 12 by means of support pins 50 andretaining clips 59, which are spaced circumferentially around the outerportion of the ring. In accordance with the present invention, the innerportion of the baflie plate 17 comprising the portion 17a, inclinesdownwardly and inwardly' to a central opening which is centered overring 42. Preferably the baffle 17, including the downwardly and inwardlyinclined portion 17a, is positioned at a spaced distance above the topof the ring 42. The central opening in the baflle ring 17 is preferablyof larger diameter than the diameter of the ring 42, as shown in thedrawings.

The flooded volume of the pot may be reduced While at the same timeimproving the operation of the burner by employing a specially shaped orcontoured bottom. More specifically, the bottom 11 may be shaped orformed to provide a depressed oil-holding channel 50 extending aroundthe outside of ring 42 immediately adjacent thereto, as shown moreclearly in FIGS. 1 and 3. The central portion of bottom 11 which isenclosed by the ring 42 preferably has a part thereof, such as the part51, which is raised above the lowest portion of channel 50, and the restthereof being at a lower level, such as the portion 52 (FIG. 3). Channel50 and bottom portion 52 are disposed so that they are in liquid flowcommunication with the oil inlet opening 37. In the illustration given,bottom portion 53 and channel 50 are in flow communication with theinner end of the sump 40 so that as the level of oil increases withinthe pot, the oil will flow from the sump 40 onto the bottom portion 52and at the same time into the channel 50.

It'will usually be preferred to form bottom 11 from a separate piece ofmetal than side wall 12. In the illustration given, bottom 11 isprovided with an attachment flange 11a which is connected to the lowerend of wall 12 by any suitable means providing a sealed joint, such asseam welding.

Operation The operation of the burner pot will be largely apparent fromthe foregoing discussion, but it may be briefly summarized as follows:

Fuel oil is supplied by gravity feed and using a constant liquid levelvalve, through the pipe 36, the terminal inclined section 36a, and theopening 37, being discharged into sump 40 onto the wick 41. At pilotfire rates, the flame will issue from the inner end of housing 21, atypical pilot fire level being indicated in FIG. 3.

The flame under pilot conditions will be stable, substantiallysmoke-free, and will not be subject to pulsation or fluttering. Theflame will be largely confined within the central passage 28 between thebaflies 25 and 26. The inner end 28 of passage 27 will serve as aflame-holding means under pilot fire conditions. Combustion productswill be recirculated through the passages 29 and 30 to be mixed with thenewly vaporized fuel and air mixture at the entrance 34 to the passage27. Since the perforations 38 are directed downwardly, air can flowdownwardly and forwardly through the bottom portions of the passages 29and 30, as indicated by the arrows in FIG. 4, while combustion productsare recirculated in the opposite direction through the upper portions ofthese passages. The recirculation flow is also indicated by arrows inFIG. 5.

The inclination of the terminal pipe section 36a tends to prevent outageof the pilot flame due to excess vaporization of the liquid fuel in thefuel inlet pipe. Because of the angle of the terminal section 36a, oilfills the inlet section to a level, as indicated at 54 in FIG. 3, beforeit can enter the opening 37. Thus, there is a very limited exposed oilsurface within the fuel inlet pipe 36 for vaporization to occur.

By discharging the incoming oil onto wick 41, even at low fuel supplyrates, as under pilot fire conditions, the incoming oil is absorbed andspread, stabilizing the vaporization rate, thereby tending to produce amore stable and quiet flame, especially in combination with the inclinedinlet pipe section 36a.

Under pilot and higher conditions, the flame issuing from the inner endof passage 27 plays on the underside of the protector strip 39. Thestrip 39 can expand forwardly without distorting the housing top wall210, and the strip also serves to protect top wall 21c against the hightemperatures produced by direct contact with the tip of the flame underpilot fire conditions, thereby further reducing the tendency of housing21 to distort even though formed of sheet metal.

As the fire rate is increased by supplying additional fuel, the flamecan move to an intermediate position, or on to a high fire position,both positions being illustrated diagrammatically in FIG. 3. Undertransition to intermediate or high fire conditions, the annular bafiie17, also referred to as the control ring, cooperates with the pilotflame ring 43 to produce a quieter, more stable, and less sooty flamethan would otherwise be obtained. Apparently, this is due torecirculation of combustion products within the lower portion of theburner, but certainly within the outer zone 49.

The specially shaped and contoured bottom 11 provides a reduced floodedvolume which makes the burner safer to operate. It is not necessary toemploy a temperaturesensing device in conjunction with the burner forshutting off the flow of oil when the burner is cold. Sufficient controlis provided by the liquid level valve. The raised central portion of theburner 51 in combination with the channel 50 provides for a smooth andeflicient operation. Flare-up and die-down effects are avoided, and asmooth transition is obtained by the gradual change in the amount ofvaporizing surface.

While in the foregoing specification this invention has been describedin relation to a specific preferred embodiment thereof and many detailshave been set forth for the purpose of illustration, it will be apparentto those skilled in the art that the invention is susceptible to otherembodiments and that certain of the details described herein can bevaried considerably without departing from the basic principles of theinvention.

We claim:

1. In combination:

(a) a burner pot for a pot-type oil burner,

said pot having an open top, a closed bottom, and a circumferential sidewall providing air inlet perforations at levels above the lower positionthereof;

(b) a pilot fire zone located adjacent a side portion of said bottom,

said pilot fire zone extending toward the center of said bottom andhaving its outer end enclosed by part of the lower portion of said sideWall;

(c) a housing within the lower portion of said pot providing Wall meansenclosing the top and sides of said pilot fire zone,

said housing having an open inner end of restricted cross section ascompared with the cross section of said housing;

(d) vertically-extending baflle means within the outer portion of saidpilot fire zone beneath said housing and dividing said outer portioninto at least two inwardly-extending passages,

one of said passages converging inwardly to an outlet within saidhousing of restricted cross sec-tion,

the other of said passages enlarging inwardly to an outlet within saidhousing of enlarged cross section,

the inner and outer end portions of said passages being in opencommunication; and

(e) separate oil and air inlet means communicating with the outerportion of said pilot fire zone.

2. The combination of claim 1 wherein the wall of said housing enclosingthe top of said pilot fire zone is formed of sheet metal, and aprotector strip of sheet metal is supported adjacent the undersidethereof by means permitting said protector strip to expand and contractindependently of said top wall.

3. The combination of claim 2 wherein said protector strip has its outerend portion rigidly attached to said top wall and its inner end portionturned upwardly over the inner end portion of said wall to form aslidable support therefor.

4. The combination of claim 1 wherein said oi-l inlet means comprises apipe extending to an opening in the lower portion of said side wallimmediately above said bottom wall, said pipe terminating in a sectionadjacent said opening which in inclined downwardly with respect to thehorizontal at an angle of from 20 to 50 degrees.

5. The combination of claim 4 wherein an oil-holding depression isprovided in said pot bottom adjacent said oil inlet opening.

6. The combination of claim 5 wherein a flat noncombustible wick isprovided within said oil-holding depression.

7. The combination of claim 1 wherein said housing extends only part ofthe way toward the center of said bottom, and a vertically-extendingring encloses a central zone in the lower portion of said pot, one sideof said ring having an opening therethrough in direct communication withthe open inner end of said housing.

8. The combination of claim 7 in which an annular bafiie plate issupported at the top of the lower portion of said pot at a spaceddistance above said housing and ring, said plate having its outerportion adjacent the pot side wall and inclining downwardly and inwardlyto an opening therethrough centered over said ring.

9. The combination of claim 8 wherein the lower portion of said ring hasopenings in the wall thereof communicating with an outer zone of saidpot beneath said baffle, the side wall of said pot providing an inletopening at a level below said bafile for introducing air into said outerzone, the opening in said baflie being of larger diameter than that ofsaid ring.

10. The combination of claim 9 wherein said bottom provides a depressedoil-holding channel extending around the outside of said ring, part ofthe portion of said bottom enclosed by said bottom being raised abovethe lowest portion of said channel and the rest being at a lower level,said channel and the said lower part of the ring-enclosed portion ofsaid bottom being in liquid flow communication with said oil inletmeans.

'11. In combination:

(a) a burner pot for a pot-type oil burner,

said pot having an open top, a closed bottom, and

a circumferential closed bottom, and a circumferential side wallproviding air inlet perforations at levels above the lower positionthereof;

(b) a pilot fire zone located adjacent a side portion of said bottom,

said pilot fire zone extending toward the center of said bottom andhaving its outer end enclosed by part of the lower portion of said sidewall;

(c) a housing within the lower portion of said pot providing wall meansenclosing the top and sides of said pilot fire zone,

said housing having an open inner end of restricted cross section ascompared with the cross section of said housing;

(d) vertically-extending baflie means within the outer portion of saidpilot fire zone beneath said housing and dividing said outer portioninto at least two inwardly-extending passages,

one of said passages converging inwardly to an outlet within saidhousing of restricted cross section, the other of said passagesenlarging inwardly to an outlet within said housing of enlarged crosssection;

(e) separate oil and air inlet means communicating with the outerportion of said pilot fire zone; and

(f) a vertically-extending ring enclosing a central zone in the lowerportion of said pot,

one side of said ring having an opening therethrough in directcommunication with the open inner end of said housing.

12. The combination .of claim 11 in which an annular bafile plate issupported at the top of the lower portion of said pot at a spaceddistance above said housing and ring, said plate having its outerportion adjacent the pot side wall and inclining downwardly and inwardlyto an opening therethrough centered over said ring.

13. In combination:

(a) a burner pot for a pot-type oil burner,

said pot having an open top, a closed bottom, and a circumferential sidewall providing air inlet perforations at levels above the lower positionthereof;

(b) a pilot fire zone located adjacent a side portion of said bottom,

said pilot fire zone extending toward the center of said bottom andhaving its outer end enclosed by part of the lower portion of said sidewall;

(c) a housing within the lower portion of said pot providing wall meansenclosing the top and sides of said pilot fire zone,

said housing having an open inner end of restricted cross section ascompared with the cross section of said housing,

said housing extending only part of the way toward the center of saidbottom;

(d) a verticallyextending ring enclosing a central zone in the lowerportion of said pot,

one side of said ring having an opening therethrough in directcommunication with the open inner. end of said housing;

(e) anannular baffle plate supported at the top of the lower portion ofsaid pot at a spaced distance above said housing ring,

said plate having its outer portion adjacent the pot side wall andinclining downwardly and inwardly to an opening therethrough centeredover said pilot ring; and

(f) separate oil and air inlet means communicating with the outerportion of said pilot fire zone.

14. The combination of claim 13 wherein the lower portion of said ringhas openings in the wall thereof communicating with an outer zone ofsaid pot beneath said bafile, the side wall of said pot providing aninlet opening at a level below said balfie for introducing air into saidouter zone, the opening in said 'bafi'le being of larger diameter thanthat of said ring.

15. The combination of claim 13 wherein said bottom provides a depressedoil-holding channel extending around the outside of said ring, part ofthe portion of said bottom enclosed by said bottom being raised abovethe lowest portion of said channel and the rest being at a lower level,said channel and the said lower part of the ring-enclosed portion ofsaid bottom being in liquid flow communication with said oil inletmeans.

16. The combination of claim 13 wherein said combination also includeslaterally-spaced, vertically-extending baffle means within the outerportion of said pilot fire zone beneath said housing and dividing saidouter portion into three inwardly-extending passages, the center one ofsaid passages converging inwardly to an outlet within said housing ofrestricted cross section, the outside two of said passages enlarginginwardly to outlets within said housing of enlarged cross section, andthe inner and outer end portions of said passages being in opencommunication.

17. In combination:

(a) a burner pot for a pot-type oil burner,

said pot having an open top, a closed bottom, and a circumferential sidewall providing air inlet perforations at levels above the lower positionthereof;

(b) a pilot fire zone located adjacent a side portion of said bottom,

said pilot fire zone extending toward the center of said bottom andhaving its outer end enclosed by part of the lower portion of said sidewall;

(c) a housing within the lower portion of said pot providing wall meansenclosing the top and sides of said pilot fire zone,

said housing having an open inner end of restricted cross section ascompared with the cross section of said housing, said housing beingformed of sheet metal;

(d) a protector strip of sheet metal supported adjacent the underside ofthe top of said housing by means permitting said protector strip toexpand and contract independently of said top wall; and

(e) separate oil and air inlet means communicating with the outerportion of said pilot fire zone.

18. In combination:

(a) a burner pot for a pot-type oil burner,

said pot having an open top, a closed bottom, and a circumferential sidewall providing air inlet perforations at levels above the lower positionthereof;

(b) a pilot fire zone located adjacent a side portion of said bottom,

said pilot fire zone extending toward the center of said bottom andhaving its outer end enclosed by part of the lower portion of said sidewall;

(c) a housing within the lower portion of said pot providing wall meansenclosing the top and sides of said pilot fire zone,

said housing having an open inner end of restricted cross section ascompared with the cross section of said housing;

(d) separate oil and air inlet means communicating with the outerportion of said pilot fire zone,

said oil inlet means comprising a pipe extending to an opening in thelower portion of said side wall immediately above said bottom wall,

said pipe terminating in a section adjacent said opening which isinclined downwardly with respect to the horizontal at an angle of from20 to 50 degrees;

(e) an oil-holding depression provided in said pot bottom wall adjacentsaid oil inlet opening; and

(f) a fiat, non-combustible wick provided within said oil-holdingdepression.

19. In combination:

(a) a burner pot for a pot-type oil burner,

said pot having an open top, a closed bottom, and

a circumferential side wall providing air inlet perforations at levelsabove the lower position thereof;

(b) a pilot fire zone located adjacent a side portion of said bottom,

said pilot fire zone extending toward the center of said bottom andhaving its outer end enclosed by part of the lower portion of said sidewall;

(c) a housing within the lower portion of said pot providing wall meansenclosing the top and sides of said pilot fire zone,

said housing having an open inner end of restricted cross section ascompared with the cross section of said housing,

said housing extending only part of the way toward the center of saidbottom;

(d) a vertically-extending ring enclosing a central zone in the lowerportion of said pot,

.one side of said ring having an opening therethrough in directcommunication with the open inner end of said housing;

(e) oil inlet means communicating with the outer portion of said pilotfire zone; and

(f) the bottom of said pot providing a depressed oilholding channelextending around the outside of said ring,

part of the portion of said bottom enclosed by said bottom being raisedabove the lowest portion of said channel :and the rest being at a lowerlevel,

said channel and the said lower part of the ringenclosed portion of saidbottom being in liquid flow communication with said oil inlet means.

References Cited by the Examiner UNITED STATES PATENTS 2,162,844 6/1939Jenson 158-91 2,537,966 1/1951 Cargile et al 158-91 2,574,358 11/1951John 15891 2,748,847 6/ 1956 Gilmore et al 15891 2,756,811 7/1956 Little158-91 3,017,924 1/1962 Jenson 158--91 3,147,796 9/1964 Mueller l5891FREDERICK KETTERER, Primary Examiner.

1. IN COMBINATION: (A) A BURNER POT FOR A POT-TYPE OIL BURNER, SAID POTHAVING AN OPEN TOP, A CLOSED BOTTOM AND A CIRCUMFERENTIAL SIDE WALLPROVIDING AIR INLET PERFORATIONS AT LEVELS ABOVE THE LOWER POSITIONTHEREOF; (B) A PILOT FIRE ZONE LOCATED ADJACENT A SIDE PORTION OF SAIDBOTTOM, SAID PILOT FIRE ZONE EXTENDING TOWARD THE CENTER OF SAID BOTTOMAND HAVING ITS OUTER END ENCLOSED BY PART OF THE LOWER PORTION OF SAIDSIDE WALL; (C) A HOUSING WITHIN THE LOWER PORTION OF SAID POT PROVIDINGWALL MEANS ENCLOSING THE TOP AND SIDES OF SAID PILOT FIRE ZONE, SAIDHOUSING HAVING AN OPEN INNER END OF RESTRICTED CROSS SECTION AS COMPAREDWITH THE CROSS SECTION OF SAID HOUSING; (D) VERTICALLY-EXTENDING BAFFLEMEANS WITHIN THE OUTER PORTION OF SAID PILOT FIRE ZONE BENEATH SAIDHOUSING AND DIVIDING SAID OUTER PORTION INTO AT LEAST TWOINWARDLY-EXTENDING PASSAGES, ONE OF SAID PASSAGES CONVERGING INWARDLY TOAN OUTLET WITHIN SAID HOUSING OF RESTRICTED CROSS SECTION, THE OTHER OFSAID PASSAGES ENLARGING INWARDLY TO AN OUTLET WITHIN SAID HOUSING OFENLARGED CROSS SECTION, THE INNER AND OUTER END PORTIONS OF SAIDPASSAGES BEING IN OPEN COMMUNICATION; AND (E) SEPARATE OIL AND AIR INLETMEANS COMMUNICATING WITH THE OUTER PORTION OF SAID PILOT FIRE ZONE.